Two powerful groups of moderate Democratic lawmakers have met with their House leaders to warn against pushing health care reform proposals too far to the left.

The New Democrat Coalition and the Blue Dogs met separately Thursday with Democratic leaders to push for legislation they could embrace.

"We made it pretty clear that there are 51 of us, and if they want our vote on health care reform, we're going to be pretty involved in writing the bill," said Rep. Mike Ross (D-Ark.), chairman of the Blue Dogs' health care task force.

The first-of-their-kind meetings signaled that it could be more difficult than many expected for the House to pass a more progressive bill as a counterweight to a more moderate version expected to come from the Senate.

Both the New Dems and Blue Dogs have been working to disabuse their leaders of that notion. In a recent letter, the Blue Dogs expressed concern about being left out of the legislation's development. Together, the two blocs represent 122 of the 218 votes need to pass legislation.

The moderates are wary of being forced to "walk the plank" and vote for a more liberal bill that is out of step with their district constituents, only to see a more moderate version forged later between House and Senate negotiators — as many expect will happen.

Moderates want a "vote everyone's interested in selling, not a vote that we have to walk away from," said a senior staffer for a New Democrat familiar with the discussion.

The leaders of both groups met with House Speaker Nancy Pelosi of California, House Majority Leader Steny Hoyer of Maryland and other leaders, including Reps. George Miller of California, Charles Rangel of New York and Frank Pallone of New Jersey — the chairmen of key committees, say those familiar with the meetings.

In the meetings, the Blue Dogs were concerned with process and how the reforms would be paid for, while the New Dems were focused on policy.

Still, both groups raised concerns over the controversial proposal to create a public insurance plan that competes with the private insurance market.

During the meeting with the New Dems, the committee chairmen made it clear that including the public plan was central to bringing costs down, according to a source familiar with the meetings.

The groups agree that the public plan can't be based on Medicare rules, that it must pay for itself and operate under the same rules that private plans do. The principles are similar to a public plan option rolled out by Sen. Chuck Schumer (D-N.Y.).

"There's a good chance if we can work out the details — because I don't think they can pass it without us — having a public plan option that can compete may be the compromise," Ross said.

But a senior leadership aide involved in the process said that Blue Dogs are going to have to make a choice.

"Do they want to pay for [health reform], or do they want to kill the public plan?" the aide said. "I don't think they're going to have the political will to do both."

The leadership suggested that the New Dems take the lead on holding six major health care organizations accountable for their promise this week to cut $2 trillion in the rate of health care growth over 10 years — an agreement that already has one of the groups backpedaling.

On Thursday, American Hospital Association President Richard Umbdenstock told his members on a conference call that the agreement had been misrepresented.

But after reports of the call became public, the hospital association and its five partners released a statement Friday that said they remain committed to cutting costs and "look forward to offering cost-savings recommendations in the weeks ahead."